1. Field of the Invention
The present invention relates to a system for vehicle safety devices such as air-bags, safety belt tightening devices and the like in a motor vehicle.
2. Description of the Prior Art
For ensuring the safety of motor vehicle passengers, there have been developed various vehicle safety devices such as air-bags, safety belt tightening devices and the like.
In a vehicle safety system including such a vehicle safety device, in order to ensure the operation of a safety device assuredly even if the battery is disabled at the time of a vehicle collision, the system is provided with an electric energy supply circuit for storing electric energy for actuating the safety device, which is called an "energy reservoir". The conventional energy reservoir has a voltage step-up circuit including an inductance element and a capacitor of large capacity, and a high output voltage derived from the voltage step-up circuit in response to the application of an ON/OFF signal is supplied to the capacitor to store the electric energy for actuating the safety device therein. Then, the electric energy stored in the capacitor is supplied to the electrically fired actuator of the vehicle safety device at the time of a vehicle collision, so that the vehicle safety device operates reliably.
Consequently, it is necessary for these devices to be constantly monitored to determine whether or not the system is in a ready condition enabling the safety device to operate assuredly upon the occurrence of a vehicle collision, and to inform the driver whenever trouble occurs. To satisfy these requirements, the conventional system has a circuit for monitoring or checking the condition of the various portions of the vehicle safety system, and a warning light mounted on a center console is turned on to inform the driver of the occurrence of trouble when a malfunction arises in the system. For enabling the driver to check whether or not the warning light itself is broken, this warning light is normally turned on only once at the beginning of vehicle operation, at the time the ignition switch is turned on. Accordingly, in the case where the warning light filament or the wire supplying current to the warning light breaks in the course of the vehicle operation, it becomes impossible to inform the driver of the occurrence of any malfunction of the safety system even if the circuit detects that there is a malfunction in the safety system.